/**
 * Definition for singly-linked list.
struct ListNode {
    int val;
    ListNode *next;
    ListNode() : val(0), next(nullptr) {}
    ListNode(int x) : val(x), next(nullptr) {}
    ListNode(int x, ListNode *next) : val(x), next(next) {}
};
 */

struct ListNode
{
  int val;
  ListNode *next;
  ListNode() : val(0), next(nullptr) {}
  ListNode(int x) : val(x), next(nullptr) {}
  ListNode(int x, ListNode *next) : val(x), next(next) {}
};

class Solution
{
public:
  ListNode *removeNthFromEnd(ListNode *head, int n)
  {
    ListNode *dummyHead = new ListNode();
    dummyHead->next = head;
    ListNode *fast = dummyHead;
    ListNode *slow = dummyHead;
    while (n-- && fast != nullptr)
    {
      fast = fast->next;
    }
    fast = fast->next;
    while (fast != nullptr)
    {
      fast = fast->next;
      slow = slow->next;
    }
    slow->next = slow->next->next;

    ListNode *result = dummyHead->next;
    delete dummyHead;
    dummyHead = nullptr;

    return result;
  }
};